BACKGROUNDThrough an RNAi synthetic lethal screen we have identified the protein SUMOylation pathway to be required for the viability of Ras mutant cancer cells.PURPOSEIn this project we aim to address the following questions: 1) the mechanism by which the inhibition of SUMOylation pathway is synthetically lethal with Ras mutation; 2) which cellular proteins are differentially SUMOylated in Ras mutant cells; and 3) How the changes in SUMOylation status of these proteins affect their function in the context of Ras mutant tumors.SIGNIFICANT MATERIALS AND METHODS1) shRNAs that target the SUMO E1 and E2 ligases and SUMO pathway proteins; 2) Stable cell lines expressing SUMO proteins and ligases; 3) mass-spectrometry protocol for identifying SUMOylated proteins in cell lysates.FY2012 ACCOMPLISHMENTContinuing our effort from FY2011, we have identified a number of candidate proteins that are differentially SUMOylated between Ras WT and mutant cells. We are currently studying the functions of these SUMOylated proteins in KRAS mutant cells. We are also investigating how SUMOylation affects the activity of these proteins.